Healthy sleep duration

7-9 hours for adults aged 18-64, 7-8 hours for those over 65, 8-10 hours for teenagers, 9-12 hours for school-age children, and infants and young children need to ensure a total sleep of 12-16 hours. However, this standard is a reference value based on statistics from a large sample. It is never a "hard passing line" that applies to all individuals. Whether the sleep duration that is suitable for you is healthy is never based on whether you have enough 8 hours.

I met an old colleague who works in content operations a while ago and complained to me that he was having a nervous breakdown recently - he used to sleep for 6 hours a day and wake up naturally without drinking coffee during the day. He read popular science and said that not sleeping enough for 8 hours will shorten your life. He forced himself to go to bed 2 hours earlier every day. As a result, he could not fall asleep until early in the morning.

In fact, the controversy over the healthy duration of sleep has been quarreling in the academic community for almost ten years. Earlier studies supporting the "fixed duration standard" were mostly based on very large-scale long-term population tracking. For example, the study published by the European Heart Journal in 2021 covered more than 100,000 respondents and was followed for more than 10 years. It was indeed concluded that respondents who sleep for less than 6 hours or more than 10 hours have a risk of cardiovascular and cerebrovascular diseases that is about 19% higher than those who sleep 7-8 hours. The risk of diabetes and cognitive decline also increases to varying degrees. This is also the most commonly mentioned conclusion in various science papers. There is nothing wrong with it, but it describes the "group average risk" and is not an accurate yardstick that can be applied to everyone.

In recent years, more and more laboratory research has begun to turn to individual differences. A 2022 paper from the Stanford Sleep Research Center clearly mentioned that about 1%-3% of people in the population carry DEC2 gene mutations, which are commonly known as "short sleep genes." These people are born with a shorter sleep duration than ordinary people. They only need 4-6 hours a day to get enough deep sleep and rapid eye movement sleep, and maintaining this duration for a long time will not cause any health damage. Correspondingly, there are a similar proportion of carriers of the "long sleep gene", who must sleep 9-10 hours a day to stay awake. If they insist on compressing the sleep time, it will lead to decreased immunity and emotional control.

Many people will ask, I don’t know if I have a genetic mutation, how can I judge whether I am getting enough sleep? In fact, you don’t need to go for genetic testing. You need to give yourself a week’s adjustment period. You don’t need to set an alarm clock, and don’t deliberately stay up late or lie in bed playing with your mobile phone. Go to bed when you feel sleepy every day, sleep until you wake up naturally, and then observe your status during the day: you don’t need to rely on coffee or energy drinks, and you won’t be in the car. If you nod unconsciously and doze off during long meetings, you won't get irritated and irritable over trivial things, and you can concentrate when remembering things and doing work, then the amount of time you sleep every day is your healthy time, even if it is 6 or 9 hours, there is no need to worry.

One thing to note here is not to regard the "tolerance" developed by long-term sleep deprivation as a natural short sleep. I have seen too many 996 young people who say that 6 hours of sleep is enough, but on the weekends they can sleep for 10 hours without an alarm clock without remembering it. This is a typical sleep debt. It is not a natural short sleep - people with short sleep genes will naturally wake up by no more than 1 hour on weekdays or weekends.

Last month, a parent of a senior in high school came to me for consultation, saying that his child could only sleep 6 hours a day in preparation for the exam. Will it leave permanent health problems? In fact, there is no need to be too nervous. Short-term sleep deprivation, ranging from a few months to six months, will not cause irreversible damage as long as you can adjust back to a normal schedule and make up for the missed sleep. What you really need to be wary of is maintaining a sleep duration lower than your own needs for three to five years, or even more than ten years, which will really increase the risk of chronic diseases.

Oh, by the way, many people are obsessed with shortening the time, but ignore the more important sleep quality. I have a friend who suffers from severe sleep apnea syndrome. He lies down for 9 hours a day and wakes up three or four times due to lack of oxygen. He is still groggy during the day. When he went to sleep monitoring, he found that the proportion of deep sleep was less than 10%, which is not as good as other people who sleep for 6 hours and account for 20% of the sleep. Instead of staring at the alarm clock to count how many hours you have slept, it is better to adjust the light and temperature in the bedroom to a comfortable temperature and avoid watching short videos before going to bed, which will be more effective in improving the quality of sleep.

I myself don't stick to the "8 hours" standard now. I usually go to bed at 12 o'clock and start at 7 o'clock on weekdays, which is exactly 7 hours. On weekends, I sometimes stay up late to watch football, and I can sleep until more than 9 o'clock the next day, which adds up to 8 and a half hours, and I don't think there is any problem. To put it bluntly, sleeping is like eating and drinking. Some people are full after eating a bowl, while others need to eat a bowl and a half. There is no need to embarrass yourself by following a unified standard. It is better to wake up comfortable and energetic during the day.